Porter etal
knit fabric



pt. 5, 1967 s. L. PORTER ETAL 3,340,134

KNIT FABRIC Filed July 31, 1959 2 sheets-sheet 1 Sept. 5, 1967 s. 1.. PORTER ETAL 3,340,134

KNIT FABRIC Filed July 51, 1959 2 Sheets-Sheet 2 United States Patent 3,340,134 KNIT FABRIC Stephen L. Porter, Harrisburg, and Calvin Auville, Dayton, Va., and Allen R. Winch, Westfield, N.J., assignors to Celanese Corporation, a corporation of Delaware Filed July 31, 1959, Ser. No. 830,771 15 Claims. (Cl. 16189) The present invention relates to the knitting of novel fabrics of low weight and relatively high strength.

This application is a continuation-in-part of our application Ser. No. 795,858, filed Feb. 26, 1959, now abandoned, the disclosure of which is incorporated herein by reference.

In our earlier application we disclose warp knit fabrics of very low weight which are especially useful as cover fabrics for sanitary napkins because of their softness, pinning strength, porosity, covering power, and other desirable properties.

It is an object of the present invention to provide additional novel knit fabrics exhibiting exceptional properties.

A further object of the invention is to provide warp knit fabrics characterized by both marked softness and resistance to running.

Other objects and advantages will become apparent in accordance with the following description and claims wherein in formulating the stitch patterns the spaces are numbered from right to left.

In accordance with one aspect of the invention there is provided a knit fabric having areas in which a run once started will propagate readily alternated longitudinally with areas in which a run will not propagate readily. The run-resistant areas may repeat relatively frequently, e.g. every few courses, or the pattern may be more intricate with a considerable length of run-prone fabric followed by a length of fabric in which run-prone and run-resistant lengths alternate at relatively short intervals.

In one suitable fabric the different areas are created by the stitch pattern employed. The stitch pattern over one or more courses is such that one or more wales are joined to adjacent wales by splittable stitches; these splittable stitches in one or more subsequent courses are replaced by non-splittable stitches, thereby preventing propagation of splitting. Conveniently the fabric may be made on a multiple bar warp knitting machine. The warps of one of the bars may form longitudinal chains or wales resistant to stretching and the warps of another bar may hold the chains together to form the fabric. Each warp of the second bar for several courses is enmeshed with only a single chain but at predetermined intervals it is enmeshed with several chains, ie it spans several wales. By contrast, if each warp of the second bar contacts only a single chain, splittable stitches are formed and it is possible to separate the fabric longitudinally between chains by unzipping it. Alternately, if each warp of the second bar spans several chains, the result is a lock stitch construction which cannot be unzipped between these chains without breaking the warp of the second bar; this construction, however, is of relatively higher weight per unit area and involves numerous closely positioned locations at which several layers of yarn are superposed, with a reduction in softness and a more coarse hand.

The present invention combines the splittable, or zip, stitch and the lock stitch to produce a fabric which is characterized by high resistance to unzipping even once a tear is begun and which is also characterized by softness substantially identical with that of a completely zip stitch construction insofar as the human body can detect. The instant constructions are characterized by high pinning strengths, defined hereinafter, exceeding 2 pounds and the cuts will generally exceeding 3 pounds even in light weight fabrics knit from yarns of considerably less than denier.

Fabrics of this construction are especially suited as covers for sanitary napkins and anywhere else that low weight of the order of less than 1 ounce per square yard (a yield of at least 16 square yards per pound), high strength, soft feel and/or attractive fabrics are desired. Thus they can constitute a backing or scrim in place of gauze for non-Wovens such as filters, battings used in making quilted fabrics, and the like. Alternatively, they may be made in narrow widths and used as decorative lace-work ribbons alone or in conjunction with plastic films, etc.

The specific end use will govern the particular construc. tion of the fabric. If it is intended to be used as a covering fabric for sanitary napkins, on suitable construction involves two sets of warps of which one is knit in chains (0-1/1-0 stitch pattern) and the other is knit to span a single chain except periodically when for a predetermined number of courses it spans more than one chain, e.g. two chains. I

In accordance with one aspect 'of the invention the warps of the second set span more than one chain or Wale, preferably only two wales in the interest of softness, more frequently than about twice in every twelve courses, and. preferably about twice in every eight courses in the in-- terest of improved appearance, increased pinning strength and resistance to accidental splitting. In accordance with a preferred embodiment the bars are each threaded 1 in 2 out and the stitch pattern of the second set of warps is (1-0, 3-4 X times) 1-0, 6-7, where X is a positive integer, preferably l in which case the pattern repeats every fourth course. The exact stitch pattern and threading will of course depend upon the closeness of the needles and the desired openness of the fabric. Another possible pattern is 1-0, 6-7, 3-4, .6-7; another is. 1-0, 6-7, 3-4, 6-7, 1-0, 3-4; an endless number of suitable patterns is possible.

In accordance with another aspect of the invention, the the warps of the second set follow a 1-0, 3-4 stitch patern, repeating every two courses, for about eighteen inches,

for example; this is a zip stitch construction. For approxi-] mately the next inch the second set of warps are knit to eight course repeats, or the stitch pattern of one or both bars may be such that all stitches are lock stitches, erg. 1-0, 3-4 for the first bar warps and 3-4, 1-0 for the second bar warps, or the like. Since the fabric when used for a napkin covering must be out about nineteen inches long, be made approximately midway along the lock stitch zone so as not to initiate unzipping. It has been found that the lock stitch zone causes the fabric to neck down; since it is often advantageous to thin down the ends of a sanitary napkin, however, cutting through the necked down lock stitch zone will automatically achieve the desired result. This fabric embodiment has an excellent appearance, a high yield and a high production speed although means must be provided to allow a 19 inch repeat and when cutting synchronization is necessary to ensure proper positioning of the cuts.

In another embodiment the run-resistant areas can be created by bonding even though the stitch pattern of these areas is similar to or even identical with that of the runprone areas. Bonding can be effected in a uniform pattern all along the fabric or it may be isolated, for example, over a one-inch length following eighteen inches of runprone length, cutting of the fabric being effected approximately midway of the nineteenth inch.

In those lengths of fabric where bonding is effected, if softness is desired advantageously bonding is carried out only over small areas. The bonding pattern may run parallel to the courses for example, involving one or more continuous straight lines or several spaced broken straight lines with the breaks staggered to insure that each Wale is bonded at some point. Alternatively the bonding can be effected along'diagonal lines, continuous or broken,

with the inclination correlated to the length of the area to be bonded and with the width to ensure at least one bond per wale. In place of straight line bonds the bonds may be effected in dots of circular or other geometric shape, either full or only peripherally, or in any other manner to achieve the desired result withdue consideration for the stresses to be encountered in using the fabric.

Bonding can be effected with an adhesive, by application of a plasticizer or diluted solvent or by heat where the fabric includes thermoplastic filamentary materials. The

composition of adhesive, plasticizer or solvent as well as the temperature of heating will of course depend upon the chemical composition of the fabric. With cellulose acetate fabrics, for example, polyvinyl acetate latex is a satisfactory adhesive; glycerol triacetate, triethyl citrate, dimethoxyethyl phthalate and methyl ethoxyethyl phthalate are satisfactory plasticizers as is aqueous acetone, acetone alone being a solvent for ordinary cellulose acetate. Bonding may be effected immediately following knitting before the fabric is taken up, as a separate operation or as the fabric is being unwound prior to being cut into shorter lengths.

In the event that the run-resistant areas are produced by bonding, the fabric may be knit several times as wide as ultimately desired, it may be bonded longitudinally at intervals corresponding to the desired width and it may be cut into narrower fabrics. When ultimately intended for sanitary napkin use wrapping of the fabric about the napkin body will position the longitudinal bond lines where they will not contact the wearer.

In accordance with another aspect of the invention one or more warp threads of each bar may be omitted at spaced intervals so that the fabric may be unzipped to produce narrow bands, either as taken up on the knitting machine or subsequently. The threading of the bars at the fabric edges will generally be somewhat different than in the body to form selvages.

In accordance with yet another embodiment predetermined warp threads, preferably of that set used for the chains, may be colored differently from the other warp threads to serve as an indicator for the front or back of the napkin about which the fabric is to be wrapped.

The fabric is preferably knit of continuous filament yarns since in that manner the necessary strength can be achieved at low deniers, low deniers being softest. The denier of the yarns generally is less than about 150 and preferably less than about 100 but usually at least denier. Because of the loop-formation of the yarns in forming chains, these chains exhibit increased strength and advantageous'ly may be made of yarns of less than about 75 denier. The transversely extending yarns, however, while preferably below about 100 denier are desirably of somewhat higher denier than the chain yarns. Where multifilament yarns are employed the filaments are generally 4 twisted together to permit processing on the knitting machine. Advantageously there are 10 or fewer turns per inch and preferably 1 or fewer turns per inch since low twist yarns, while less expensive, give softer fabrics and more cover than high twist yarns.

Advantageously the individual filaments of the yarns are less than about 20 and preferably less than about 5 denier since the lower deniers are softer. The chemical composition of the yarns may vary widely and, for example, may constitute rayon, nylon, polyesters such as polyethylene terephthalate, polymers and/ or copolymers of olefins or vinyls such as ethylene, propylene, vinyl chloride, vinylidene chloride, .acrylonitrile, and the like. Preferably, however, the yarns comprise organic acid esters of cellulose such as the lower alkanoic acid esters, e.g. cellulose acetate. Cellulose acetate is desirable because of its softness,

its inertness, and its balance of hydrophilic and hydrophobic properties, i.e. a material will not be suitable which is so hydrophobic as to resist penetration of aqueous fluids or so hydrophilic that it will wick up the fluid rather than permitting the fluid to pass into deeper layers of the napkin intended for absorbency.

Another advantage of cellulose acetate is that it can easily be adhered to the substrate without stiffening, e.g. as by spraying the substrate lightly with a solvent or plasticizer. Also, cellulose acetate is less expensive than other continuous filamentary materials of comparable low denier.

This invention will be further described with reference to the accompanying drawings, wherein:

FIG. 1 is a diagrammatic illustration of the construction of one fabric;

FIG. 2 is a diagrammatic illustration of another fabric;

FIG. 3 is a plan view of another fabric;

FIG. 4 is a schematic plan view of still another knit fabric showing lines of bonding;

FIG. 5 is a schematic plan view of another knit fabric with a different pattern of bond lines. 7

Referring now more particularly to the drawings, in FIG. 1 there is shown a fabric comprising wales, warp yarns or chains 11 to 15 all from the same bar (not shown) which is threaded 1 in 2 out. The fabric also includes warps 16 to 20 which extend predominantly transversely and which are from a second bar (not shown) also threaded 1 in 2 out. Taking warp 18, for example, in going from course a to b it crosses warp 13; in going to course c warp 18 crosses warp 13 and 12 and ties them together; warp 18 recrosses warps 12 and 13 and the cycle then repeats, i.e. there is a four course repeat. It will be apparent that the stitch pattern of the warps 11 to 15 is 0-1, l-O while that of warps 16 to 20 is l-O, 3-4, 1-0, 6-7.

FIG. 2 shows another fabric in which the warps 21 to 25 are identical in stitch pattern to warps 11 to 15 of FIG. 1. The bar carrying warps 26 to 30 is threaded the same as that carrying warps 16 to 20 in FIG. 1 but the stitch pattern is slightly different. Specifically, there are eight courses to each repeat with each warp crossing two chains in two courses and for six courses crossing only one chain, e.g. 1-0, 3-4, 1-0, 3-4, 1-0, 3-4, l-O, 6-7 or (l-O, 3-4 three times) 1-0, 6-7. The fabric can be separated relatively easily between wales from courses d to but the separation cannot continue through courses c or k without breaking some warps. More particularly the splittable stitches in courses d to comprise a series of loops which project from each chain successively in alternate directions. Considering warps 28 and 29, for example, the loop at course d of warp 28 extends through the loop at course e of warp 29 which in turn extends through the loop at course 1 of warp 28, etc.

FIG. 3 shows a fabric including elongated portions 31' alternated with shorter areas 32. The portions 31 are made up of zip stitchconstruction, e.g. 1-0, 3-4 for the transversely extending warps'while the portions 32 are designed to prevent propagation of a run as by being made up in whole or in part of lock stitches or by being bonded to prevent separation of the warps.

FIG. 4 shows diagonal lines of bonding 33 on a fabric 34 while FIG. 5 shows another pattern comprising discontinuous bond lines 35 on a fabric 36. Fabric 36 also includes longitudinal bond lines 37 along which the fabric may be cut to narrower widths without producing'ends which will fray.

The invention will be further described in the following illustrative examples.

EXAMPLE I A fabric whose body has the construction shown in' FIG. 1 is produced on a tricot machine having 28 needles per inch and a 3 in 1 out (1 in 2 out 70 times) 1 in 1 out- 038 turn per inch. The threading of the bar carrying warp 16 to 20 is (1 in 2 out 72 times) 1 in 7 out and these warps are made of 55/0.3S/22 (55 denier, 0.38 turns per inch, 22 fils) cellulose acetate. The yield of the resulting fabric is 28.75 square yards per pound; there are 16 courses per inch, i.e. 30 inches per rack of 480 courses, and 12 wales per inch. For each 30 inches of fabric 96 inches of warp 11 to 15 are fed and 140 inches of warps 16 to 20. The fabric is 7 inches wide including narrow selvages (not shown in the drawing) but narrower or wider ribbons can be produced by obvious modification. If the threading patterns indicated are repented across the machine, e.g. twenty-one times across the width of a 168 inch machine, twenty-one identical fabrics will be produced simultaneously.

Notwithstanding its very high yield, the pinning strength of this fabric is 3.1 pounds. The pinning strength is determined by clamping one end of a fabric sample between a pair of jaws mounted at a fixed location on a rod. Another pair of jaws is mounted on a carriage capable of sliding along the rod; the second pair of jaws had two L- shaped pins projecting therefrom and spaced one-half inch laterally from one another. The pins extend toward the first pair of jaws and then stick up through the fabric. A weight is mounted on the second pair of jaws and the rod is tilted to vary the tension in the fabric, the fabric wales running parallel to the rod. The pinning strength is the vector of the weight acting along the rod when the pins tear the fabric. Any other tensile testing machine meeting ASTM D765 3 requirements, suitably modified with pins, can be similarly employed.

EXAMPLE II If the warps 11 to 15 and 16 to 20 in Example I are respectively replaced by 55/22 (55 denier, 22 fils) and 75/50 low twist cellulose acetate yarns the yield is 22 square yards per pound.

EXAMPLE III A fabric having the same appearance in the body and heavier selvages than in FIG. 1 is produced from low twist cellulose acetate yarns of 55 denier and 22 fils. The threading of the front bar which carries warps 11 to 15 is2in 1 out2in2out (1in2out88times) 3in 6out [repeat foregoing 6 times] 2 in 1 out 2 in 2 out (1 in 2 out 79 times) 3 in 5 out [repeat foregoing 12 times] and that of the back bar is (1 in 2 out 90 times) 1 in 9 out [repeat foregoing 6 times] (1 in 2 out 81 times) 1 in 8 out [repeat foregoing 12 times]. The stitch patterns are the same as in Example I. There are simultaneously produced six fabrics 8.25 inches wide and twelve fabrics 7.5 inches wide, having 16 courses per inch (30 inches per rack), 12 wales per inch and a yield of about 27 square yards per pound. For each rack 96 inches of front bar warps are needed and 140 inches of back bar warps. The pinning strength is about 3.7 pounds.

EXAMPLE IV Example I is repeated with the sole exception that the stitch pattern of the back bar is changed to thatshown in FIG. 2. The length of warps 26 to 30 to knit 30 inches is only 128 inches and the yield is 29 square yards per pound.

EXAMPLE V 55/22 and 75/50 cellulose acetate yarns are substituted for the front and back bar yarns, respectively, of Example IV. The fabric yield is 23 square yards per pound. The pinning strength is about 4.4 pounds.

EXAMPLE VI 6 to 124 and the yield increased to 29.5 square yards per pound. The pinning strength is about 2.6 pounds.

EXAMPLE VII With front and back bar threadings of 1 in 2 out and with a stitch pattern of '01, l0 for the front bar and 1-0, 3-4 for the back bar a fabric is knit of 55/ 22 front bar warps and 75/20 back bar warps, all of cellulose acetate. There are 12 wales per inch, 17 courses per inch, i.e. 28 inches per rack, a yield of 25 square yards per pound, 94 inches of the front bar warps per rack and inches of back bar warps per rack. To the fabric at 19 inch repeats there is applied over a distance of 1 inch along 45 diagonal lines 0.125 inch Wide and separated from one another by 0.375 inch an aqueous latex containing 35% by weight of polyvinyl acetate. Solid lines of latex 0.25 inch wide are printed in longitudinal direction of the fabric at 7 inch widths. The fabric is dried in hot air at 250 F. and is then slit longitudinally through the solid latex lines and transversely through the diagonal bonded areas.

EXAMPLE VIII Repeating Example I except that all yarns are 45 denier l3 fils cellulose acetate, the yield is increased to 30.5 square yards per pound and the pinning strength is 3.2 pounds.

It is to be understood that the foregoing detailed description is merely given by way of illustration and that many variations may be made therein without departing from the spirit of our invention.

Having described our invention, what We desire to secure by Letters Patent is:

1. A knit fabric of zig stitch construction weighing less than about 1 ounce per square yard, said fabric having areas in which a run once started will propagate alternated longitudinally with bonded areas which will not propagate a run, said bonded areas at some point extending across each wale.

2. A knit fabric of zig stitch construction having lines of splittable stitches in which splitting once started will propagate alternated longitudinally with bonded areas in which splitting will not propagate, portions of said bonded areas extending across said lines to limit the splitting along said lines.

3. A fabric according to claim 2, wherein said bonded areas are laid out on spaced lines extending transversely of the wales of said fabric.

4. A fabric according to claim 2, wherein said bonded areas are laid out on spaced diagonal lines extending transversely of the wales and courses.

5. A fabric according to claim 2, wherein said bonded areas are laid out on staggered broken lines extending parallel to the courses.

6. A fabric according to claim 2, knit of cellulose acetate yarns.

7. An open mesh warp knit fabric comprising two sets of warps, one of said sets being in the form of a plurality of spaced, parallel longitudinally extending knitted chains, the other of said sets being in the form of a series of threads deflected left and right through said parallel chains, said threads extending, in a repeat pattern back and forth across a single chain, and then back and forth across a single chain and an adjacent chain, and forming loops between adjacent parallel chains, the loops of said deflected threads being interlaced with loops of adjacent deflected threads.

8. A fabric according to claim 7, including at least one indicator wale colored dilferently from at least one of its adjacent wales.

9. A fabric according to claim 7, wherein said transversely extending yarns engage only one chain yarn for two courses and engage two chain yarns over the next two courses.

10. A fabric according to claim 7, wherein said yarns are less than about 150 denier, said fabric weighing less than about 1 ounce per square yard.

11. A fabric according to claim 7, wherein said yarns are multifilament cellulose acetate yarns. v

12. The warp knit fabric in claim 7, wherein said threads are less than about 150 denier, and a said fabric weighs less than about 1 ounce per square yard.

13. An open mesh warp knit fabric weighing less than about 1 ounce per square yard and comprising a plurality of spaced, parallel longitudinally extending multifilament knitted chain yarns of less than about 100 denier, holding together a plurality of essentially transversely extending multifilament yarns of less than about 100 denier, said latter yarns being deflected left and right through said parallel chains, said yarns extending, in a repeat pattern back and forth across a single chain, and then back and forth across a single chain and an adjacent chain, and forming loops between adjacent parallel chains, the loops of said deflected yarns being interlaced with loops of adjacent deflected yarns.

14. The fabric of claim 13, said yarns comprising cellulose acetate and said fabric having a pinning strength of at least 2 pounds.

15. A.warp knit fabric weighing less than about 1 ounce per square yard and comprising a plurality of longitudinally extending multifilament chain yarns of less than about 100 denier holding together a plurality of essentially transverse extending multifiIament yarns of less than about denier, said transversely extending yamsover some courses engaging only one ichain yarn and over other courses engaging more than one chain yarn, said longitudinally extending yarns having 'a stitch'pattern of 0-1, 1-0 and said transversely extending yarns having a stitch pattern of (10, 3-4 X times) 1(), 6-7, where X is a positive integer, the threading to produce said fabric being 1 in 2 out for both bars of the machine for producing saidfabric.

References Cited UNITED STATES PATENTS 903,895 11/1908 Schulz 128-290 1,650,208 11/ 1927 Hanes 66-1 1,829,231 lO/ 1931 Mergentime 66-170 2,067,961 1/ 1937 Williams 128290 2,177,425 10/1939 Barker 66-172 X 2,433,279 12/1947 Johnson 66195 X FOREIGN PATENTS 541,414 10/ 1955 Belgium.

787,949 12/ 1957 Great Britain. 803,787 10/ 8 Great Britain.

RICHARD A. GAUDET, Primary Examiner. 

1. A KNIT FABRIC OF ZIG STITCH CONSTRUCTION WEIGHING LESS THAN ABOUT 1 OUNCE PER SQUARE YARD, SAID FABRIC HAVING AREAS IN WHICH A RUN ONCE STARTED WILL PROPAGATE ALTERNATED LONGITUDINALLY WITH BONDED AREAS WHICH WILL NOT PROPAGATE A RUN, SAID BONDED AREAS AT SOME POINT EXTENDING ACROSS EACH WALE. 